None.
This invention relates in general to drive systems for all-wheel drive vehicles. In particular, the present invention relates to a drive system in which one power source, or engine, is connected to two separate transaxles arranged in a parallel relationship, one transaxle having a hydrostatic transmission associated with the front axle and drive wheel or wheels and the second transaxle having a hydrostatic transmission associated with the rear axle and drive wheel or wheels. The drive system further has a single shifter mechanism for operating the front and rear hydrostatic transmissions in harmony to provide an all-wheel drive, non-skid vehicle.
All-wheel drive vehicles, whether three wheeled, four wheeled or others, commonly comprise a vehicle power source and drive train, with the power source transmitting the driving force to the various individual wheels of the vehicle through a transmission. These vehicles are well known in the prior art and are primarily designed for use in difficult terrain or difficult driving conditions. It is an object of all such vehicles to provide improved traction and handling in such conditions and it is therefore a common problem in such vehicles to transmit the driving force from the power source to each of the wheels equally without any sacrifice of performance in one or more of the wheels. Herein, a novel drive system for all-wheel drive vehicles is disclosed in which a single power source, or engine, and a single shifter mechanism are utilized to power and shift, in harmony, two separate hydrostatic transmissions.
U.S. Pat. No. 4,819,508 discloses a drive system in which a single power source, i.e. engine, is mounted between separate left and right hydrostatic transmissions that control, independently, the left and right final drive wheels. The engine""s output shaft retains two wheels that each receive a belt. The belt associated with one wheel communicates with the input shaft of the left hydrostatic transmission, while the belt associated with the other wheel communicates with the input shaft of the right hydrostatic transmission. Thus, the single engine transfers power to two separate, left and right transmissions that in turn communicate with the left and right drive wheel or wheels of the vehicle. The separate left and right final drive wheels, through their associated transmissions, can be variably controlled through the operator""s choice in order to accomplish forward, reverse, or steering motion.
The present invention is directed towards a somewhat similar drive system in that a single power source is associated with a pair of hydrostatic transmissions. However, in the present invention, the power source is mounted so that it will power separate front and rear hydrostatic transmissions that control, respectively, a front axle and associated wheel or wheels and a rear axle and associated wheel or wheels to provide an all-wheel drive vehicle. Further, the present invention is directed towards a drive system, wherein these drive train entities are placed in a parallel relationship and are interconnected with a shifter mechanism that imposes cooperative, simultaneous, and continuous behavior between the front and rear transmissions.
In such a vehicle, it should be readily apparent to those of ordinary skill in the art that it is necessary for the separate hydrostatic transmissions to always operate in harmony if satisfactory traction, handling and non-skid operation are to be accomplished. Heretofore in the art, conventional designs for all-wheel drive vehicles have provided single components and controls for drive train entities wherein these components control functions of the drive train entities before distributing power to those final drive components. There has been no drive system designed that accomplishes all-wheel drive in the manner herein described, and, thus, there exists a need in the art to provide an all-wheel drive vehicle that connects separate hydrostatic transmissions to a common power source wherein, further, the separate transmissions can be operated in harmony while the power from the single engine is being distributed to the final drive components.
It is therefore an object of the present invention to provide a drive system for an all-wheel drive vehicle wherein a single power source, hereinafter referred to as an engine, connects multiple separate hydrostatic transmissions.
It is another object of the present invention to provide a drive system for an all-wheel drive vehicle, as above, wherein a hydrostatic transmission is associated with each in-line axil.
It is another object of the present invention to provide a drive system for an all-wheel drive vehicle, as above, wherein a first transmission is associated with a front axle of the vehicle and a second transmission is associated with a rear axle.
It is yet another object of the present invention to provide a drive system for an all-wheel drive vehicle, as above, wherein the drive system includes a shifting mechanism that can operate all separate transmissions in harmony.
In general, these and other objects of the present invention that will become apparent from the description that follows are accomplished by a drive system for an all-wheel drive vehicle having a front hydrostatic transmission and associated front gearing system, a rear hydrostatic transmission and associated rear gearing system, an engine that supplies power to both the front and rear hydrostatic transmissions, and a shifting mechanism connected to both of the front and rear hydrostatic transmissions and capable of shifting the hydrostatic transmissions substantially simultaneously and in harmony.
A preferred exemplary drive system for an all-wheel drive vehicle incorporating the concepts of the present invention is shown by way of example in the accompanying drawings without attempting to show all the various forms and modifications in which the invention might be embodied, the invention being measured by the appended claims and not by the details of the specification.